1. Field of the Invention
The present invention relates to a hydrogen separation membrane and a selectively permeable membrane reactor. More particularly, the present invention relates to a hydrogen separation membrane that exhibits excellent hydrogen permeability and durability, and a selectively permeable membrane reactor using the hydrogen separation membrane.
2. Description of Related Art
A large amount of hydrogen gas has been used as a petrochemical basic material gas. Hydrogen gas has also attracted attention as a clean energy source. Hydrogen gas used for such purposes is produced from hydrocarbons (e.g., methane, propane, butane, or kerosene) or oxygenated hydrocarbons (e.g., methanol) as a main raw material gas by utilizing a reforming reaction, a partial oxidation reaction, an self-heating reaction, a decomposition reaction, or the like. Hydrogen gas is also produced by subjecting by-product carbon monoxide and water to a shift reaction. Hydrogen thus produced can be separated and collected by utilizing a selectively permeable membrane (e.g., palladium alloy membrane) that selectively allows hydrogen to pass through, for example.
As such a separation membrane, a hydrogen separation membrane formed using palladium or a palladium alloy that contains palladium and another metal (e.g., silver, copper, gold, or a rare earth element) has been used (see Patent Documents 1 to 5 and Non-patent Documents 1 to 4, for example). Such a hydrogen separation membrane is produced so that the entire membrane is formed of an almost uniform palladium alloy from the viewpoint of the production method.    Patent Document 1: U.S. Pat. No. 3,439,474    Patent Document 2: U.S. Pat. No. 3,350,845    Patent Document 3: Japanese Patent No. 3377731    Patent Document 4: JP-A-2001-46845    Patent Document 5: U.S. Pat. No. 3,155,467    Non-patent Document 1: J. Phys. Chem., 74 (1970), pp. 503-511    Non-patent Document 2: J. Appl. Phys., 37 (2) (1966), pp. 715-721    Non-patent Document 3: Russ. J. Phys. Chem., 45 (1971), pp. 621-623    Non-patent Document 4: J. Less-Common Metals 39 (1975), pp. 293-308